Downing Street has confirmed that British Prime Minister, Mr Tony Blair, used a trip to the Czech Republic to promote jet fighters produced by a company which has donated money to the Labour Party.
But a spokesman insisted there was nothing untoward in his actions, saying the Prime Minister "makes no apology for promoting Britain and British business".
Mr Blair's brief visit to Czech capital Prague was squeezed in between his return from talks with US President George Bush in Texas and his attendance at the Queen Mother's funeral last Tuesday.
Downing Street said that the key issue on the agenda for talks with Czech Prime Minister Milos Zeman was European Union enlargement.
But a spokesman said that other bi-lateral issues were discussed, including the proposed purchase of 24 JAS-39 Gripen jets by the Czech government.
The jets are produced by an Anglo-Swedish consortium including BAe Systems, which paid £12 million to sponsor the Mind Zone at the Millennium Dome and donated more than £5,000 to Labour in 1998-99 and 1999-2000.
Shadow Cabinet Office minister Tim Collins told the Independent on Sunday: "Once again, the Government in general and the Prime Minister in particular is found to have undertaken extraordinary efforts on behalf of an organisation which has done favours for the Labour Party.
"Whatever the justifications for each of these cases may be, it is now imperative that the Committee on Standards in Public Life should consider urgently the need for the construction of a new independent mechanism by which the public can be satisfied that a full examination of the evidence is carried out to establish no impropriety has occurred."
PA